Alternative Growing Medium for Indoor Living Walls to Foster the Removal Efficiency of Volatile Organic Compounds

Increasing urbanization trends led to growing concerns regarding human health risks linked to long-time exposure to poor indoor air quality.Volatile Organic Compounds (VOCs), e.g., formaldehyde and benzene, are the most significant pollutants in indoor environments due to the high number of sources contributing to increase their concentration. Vertical Greening Systems (VGSs) have been proven as space-efficient nature-based solutions (NBS) using the ability of ornamental plants in removingVOCs.Growing media and rhizosphere community often play a pivotal role in removing indoor VOCs, especially in active biofilters. Although horticultural substrates are often overlooked in VGSs’ applications, an increasing number of studies focus on: (i) investigating sustainable opportunities provided by organic materials to produce alternative growing media; and, (ii) exploring compositions of substrates to maximize VGSs phytoremediation efficiency. This work presents preliminary results on the influence of almond shells as an alternative growing medium for VGSs on the removal efficiency of formaldehyde. For that, a VGS module with almond shells as substrate and a single species of ornamental plant was placed in a sealed chamber – specially designed to recirculate the air contaminated by formaldehyde through the module acting as an active biofilter. The system produced a clear reduction of the formaldehyde concentration, and the plants developed correctly with the substrate. Green buildingintegrated systems are multifunctional NBS which address challenges such as human wellbeing and circularity at local scale. Using organic growing media to improve the biofiltration capability of these systems is a promising alternative towards successful implementation in the built environment.